Demo (today; free; currently only available to Gold Members) - Green Day: Rock Band - includes two songs: Welcome To Paradise and Boulevard Of Broken Dreams - When you exit the demo, you're treated to the revelation that Rock Band 3 (which is coming this fall) will include keyboards as a playable instrument

Also, the Rock Band 3 keyboard I mentioned earlier in this thread may, in fact, be a keytar. That same article also claims there will be a "pro" mode, which "will require proper technique, and may lead to actual skills on guitars and bass. How this will work isn't known, but it's possible Mad Catz may create a product that more closely mimics an actual guitar."